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Introduction
For the past decade, cardiac troponins I and T have replaced Creatine kinase-MB (CK-MB) as the diagnostic biomarker for acute coronary syndromes (ACS) due to their superior sensitivity and specificity [1] . In addition, cardiac troponin levels rise and remain elevated for up to 2 weeks after the onset of chest pain, thus providing a longer window for recent-past diagnosis of ACS than CK-MB levels, which return to baseline levels in 1 to 3 days. A large study conducted on 29357 ACS patients from the CRUSADE registry supported the utilization of troponin as the sole marker of myocardial injury. The study found that only 10% (2988/29357) of cases were discordant (ie, troponin T normal, CK-MB elevated) and concluded that an elevated CK-MB alone did not offer additional prognostic value [2] .
However, CK-MB is still ordered along with troponin in many hospitals, perhaps as a combination of challenges in convincing physicians that troponin alone is sufficient in most ACS settings and CK-MB's clinical utility in certain settings such as diagnosing reinfarction in patients with a recent admission for ACS [1] .
In March 2011, Massachusetts General Hospital (MGH, Boston, MA), which cofounded Partners HealthCare alongside our institution, changed their hospital guidelines to restrict CK-MB ordering to only post-percutaneous coronary intervention and post-cardiac surgery patients [3] . In an effort to sustain results, MGH implemented educational alerts in their computerized provider order entry (OE) system, which reminded providers of the new guidelines at the time of ordering and tracked those that deviated from the guidelines. Their interventions decreased the number of CK-MB tests ordered by 87% from 1106 to 139 per month [3] . Other institutions including the Mayo Clinic and the University of Maryland have also removed CK-MB from their test menus [4] . However, few studies have examined both the clinical and financial impacts of removing CK-MB [5] .
Based on guidelines by several groups [6,7] and a growing number of studies highlighting the superiority of TnT over CK-MB in the diagnosis of ACS [1,8-10] , our institution removed the CK-MB option from electronic ordering templates and paper test requisitions in the emergency department (ED). We then studied the clinical and financial effects of this intervention by reviewing 6 months of preintervention...